1. Technical Field
Embodiments of the present invention relate to a medium speed detection device and to a printing apparatus that includes the medium speed detection device.
2. Related Art
In printing apparatuses, a scheme of analyzing image data obtained by imaging a sheet-shaped medium which is being transported and detecting a displacement amount (transport amount) of the medium (which is also referred to as a “real-image photography scheme”), as disclosed in JP-A-2013-231658, is known as a configuration for precisely transporting a sheet-shaped medium (a sheet or a film).
In the real-image photography scheme of JP-A-2013-231658, it is difficult to accelerate an imaging repetition speed. The difficulty in accelerating the imaging repetition speed becomes increasingly evident as the transport speed is further accelerated. In other words, the ability to increase the transport speed and precisely transport the sheet-shaped medium is limited by the imaging repetition speed.
Methods of widening a one-time imaged area and causing a captured image to have a high definition have been considered as solutions to this problem. Realizing these methods, however, is problematic because the sizes and costs of an imaging system device and an optical system device are increased to achieve these methods. Even when a given transport speed is accelerated in such a configuration where an imaged area is widened and an image is captured in a high definition, it is still necessary to increase the size and cost of a new apparatus in a case in which the transport speed is further accelerated. Therefore, The ability to increase the transport speed by widening the imaged area and capturing the image in high definition is limited. For this reason, it is preferable to further improve a configuration for detecting the speed of a medium which is being transported.